Application keeps quitting or destroying the root QML object?

The above source code, after a bit shuts down printing to console '[FILE] ReferenceError: parent is not defined' for each file. Normally it happens while update a ListView using data from LocalStorage or prosaic-download-queue.cpp, but it currently happens when the script adds a couple of items to prosaic-download-queue.cpp.

As it does not crash, I'm having a hard time finding out what the issues is with the code. I have seen it happen with QT 5.9/5.10/5.11, as well with mingw, vc++ and linux gcc. I hoping that someone knows the cause or how to find it.